Authority exists when two people (or groups) agree upon an authoritative relationship for a mutually beneficial purpose.
There are lots of relationships like this in life:
In these relationships, one person holds the authority based on their (assumed) fitness to do so: advanced knowledge, skills, abilities, resources, ownership. The criteria is there, even if it isn’t good criteria.
That’s important, because having criteria at all is an acknowledgement of the fact that valid authority does not exist on and inherent basis but on an agreed-upon set of criteria.
Sometimes the criteria is good and the agreement is assumed due to the nature of one person/group: It wouldn’t be safe for the two-year-old to be calling the shots in a family relationship.
Sometimes the criteria is good and the agreement must be explicit: And it wouldn’t make sense for the apprentice to tell the master what to do.
Often, the criteria is bad, very bad.
Sometimes the criteria is not clearly stated: Watch out for this.